Re: [PATCH v18 0/7] RISC-V IPI Improvements

[Anup Patel]

Hi Marc and Palmer,

On Tue, Mar 28, 2023 at 9:22 AM Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:
>
> This series aims to improve IPI support in Linux RISC-V in following ways:
>  1) Treat IPIs as normal per-CPU interrupts instead of having custom RISC-V
>     specific hooks. This also makes Linux RISC-V IPI support aligned with
>     other architectures.
>  2) Remote TLB flushes and icache flushes should prefer local IPIs instead
>     of SBI calls whenever we have specialized hardware (such as RISC-V AIA
>     IMSIC and RISC-V SWI) which allows S-mode software to directly inject
>     IPIs without any assistance from M-mode runtime firmware.
>
> These patches were originally part of the "Linux RISC-V ACLINT Support"
> series but this now a separate series so that it can be merged independently
> of the "Linux RISC-V ACLINT Support" series.
> (Refer, https://lore.kernel.org/lkml/20211007123632.697666-1-anup.patel@xxxxxxx/)
>
> These patches are also a preparatory patches for the up-coming:
>  1) Linux RISC-V AIA support
>  2) Linux RISC-V SWI support
>
> These patches can also be found in riscv_ipi_imp_v18 branch at:
> https://github.com/avpatel/linux.git
>
> Changes since v17:
>  - Resolved merge conflicts and rebased on Linux-6.3-rc4
>
> Changes since v16:
>  - Rebased on Linux-6.3-rc1
>  - Dropped PATCH3 and PATCH9 since these patches are already merged
>  - Added Palmer's Acked-by
>
> Changes since v15:
>  - Rebased on Linux-6.2-rc2
>  - Added Reviewed-by and Tested-by tags to some of the patches.
>
> Changes since v14:
>  - Minor fixes in commit description of PATCH3 (as suggested by tglx)
>  - Don't disable parent IPI when CPU goes offline for SBI IPI driver and
>    CLINT driver in PATCH4.
>  - Include Apple AIC driver changes from Marc Z as PATCH9
>
> Changes since v13:
>  - Included changes suggested by Marc Z in PATCH3
>  - Use chained handlers in PATCH4
>  - Added new PATCH8 to have empty irq_eoi() in RISC-V INTC driver. This
>    avoids the unnecessary mask/unmask dance at time of handling interrupts.
>
> Changes since v12:
>  - Rebased on Linux-6.1-rc7
>  - Bring-back the IPI optimization in ipi_mux_send_mask() for PATCH3
>  - Call ipi_mux_send() for one target CPU at a time in PATCH3
>
> Changes since v11:
>  - Removed ipi_mux_pre/post_handle() callbacks in PATCH3
>  - Removed sturct ipi_mux_ops in PATCH3
>  - Removed parent_virq and data pointer from everywhere in PATCH3
>  - Removed struct ipi_mux_control in PATCH3
>  - Improved function signature of ipi_mux_send() callback in PATCH3
>  - Used unsigned type with atomic operation in PATCH3
>
> Changes since v10:
>  - Rebased on Linux-6.1-rc5
>  - Drop the "!(pending & ibit)" check in ipi_mux_send_mask() of PATCH3
>  - Disable local interrupts in ipi_mux_send_mask() of PATCH3 because we
>    can be preempted while using a per-CPU temporary variable.
>
> Changes since v9:
>  - Rebased on Linux-6.1-rc3
>  - Updated header comment block of ipi-mux.c in PATCH3
>  - Use a struct for global data of ipi-mux.c in PATCH3
>  - Add per-CPU temp cpumask for sending IPIs in PATCH3
>  - Drop the use of fwspec in PATCH3
>  - Use static key for ipi_mux_pre_handle() and ipi_mux_post_handle()
>    in PATCH3
>  - Remove redundant pr_warn_ratelimited() called by ipi_mux_process()
>    in PATCH3
>  - Remove CPUHP thingy from ipi_mux_create() in PATCH3
>
> Changes since v8:
>  - Rebased on Linux-6.0-rc3
>  - Use dummy percpu data as parameter for request_percpu_irq() in PATCH4.
>
> Changes since v7:
>  - Rebased on Linux-6.0-rc1
>  - Use atomic operations to track per-CPU pending and enabled IPIs in PATCH3.
>    (Note: this is inspired from IPI muxing implemented in
>     drivers/irqchip/irq-apple-aic.c)
>  - Made "struct ipi_mux_ops" (added by PATCH3) flexible so that
>    drivers/irqchip/irq-apple-aic.c can adopt it in future.
>
> Changes since v6:
>  - Rebased on Linux-5.19-rc7
>  - Added documentation for struct ipi_mux_ops in PATCH3
>  - Dropped dummy irq_mask()/unmask() in PATCH3
>  - Added const for "ipi_mux_chip" in PATCH3
>  - Removed "type" initialization from ipi_mux_domain_alloc() in PATCH3
>  - Dropped translate() from "ipi_mux_domain_ops" in PATCH3
>  - Improved barrier documentation in ipi_mux_process() of PATCH3
>  - Added percpu check in ipi_mux_create() for parent_virq of PATCH3
>  - Added nr_ipi parameter in ipi_mux_create() of PATCH3
>
> Changes since v5:
>  - Rebased on Linux-5.18-rc3
>  - Used kernel doc style in PATCH3
>  - Removed redundant loop in ipi_mux_process() of PATCH3
>  - Removed "RISC-V" prefix form ipi_mux_chip.name of PATCH3
>  - Removed use of "this patch" in PATCH3 commit description
>  - Addressed few other nit comments in PATCH3
>
> Changes since v4:
>  - Rebased on Linux-5.17
>  - Includes new PATCH3 which adds mechanism to multiplex a single HW IPI
>
> Changes since v3:
>  - Rebased on Linux-5.17-rc6
>  - Updated PATCH2 to not export riscv_set_intc_hwnode_fn()
>  - Simplified riscv_intc_hwnode() in PATCH2
>
> Changes since v2:
>  - Rebased on Linux-5.17-rc4
>  - Updated PATCH2 to not create synthetic INTC fwnode and instead provide
>    a function which allows drivers to directly discover INTC fwnode
>
> Changes since v1:
>  - Use synthetic fwnode for INTC instead of irq_set_default_host() in PATCH2
>
> Anup Patel (7):
>   RISC-V: Clear SIP bit only when using SBI IPI operations
>   irqchip/riscv-intc: Allow drivers to directly discover INTC hwnode
>   RISC-V: Treat IPIs as normal Linux IRQs
>   RISC-V: Allow marking IPIs as suitable for remote FENCEs
>   RISC-V: Use IPIs for remote TLB flush when possible
>   RISC-V: Use IPIs for remote icache flush when possible
>   irqchip/riscv-intc: Add empty irq_eoi() for chained irq handlers

There were merge conflicts with Linux-6.3-rc4 which are resolved
in this series.

It would be great if this series can be considered for Linux-6.4

Thanks,
Anup

>
>  arch/riscv/Kconfig                |   2 +
>  arch/riscv/include/asm/irq.h      |   4 +
>  arch/riscv/include/asm/sbi.h      |   9 +-
>  arch/riscv/include/asm/smp.h      |  49 ++++++---
>  arch/riscv/kernel/Makefile        |   1 +
>  arch/riscv/kernel/cpu-hotplug.c   |   3 +-
>  arch/riscv/kernel/irq.c           |  21 +++-
>  arch/riscv/kernel/sbi-ipi.c       |  77 ++++++++++++++
>  arch/riscv/kernel/sbi.c           | 100 +++--------------
>  arch/riscv/kernel/smp.c           | 171 +++++++++++++++---------------
>  arch/riscv/kernel/smpboot.c       |   5 +-
>  arch/riscv/mm/cacheflush.c        |   5 +-
>  arch/riscv/mm/tlbflush.c          |  93 +++++++++++++---
>  drivers/clocksource/timer-clint.c |  65 +++++++++---
>  drivers/irqchip/Kconfig           |   1 +
>  drivers/irqchip/irq-riscv-intc.c  |  71 ++++++++-----
>  16 files changed, 429 insertions(+), 248 deletions(-)
>  create mode 100644 arch/riscv/kernel/sbi-ipi.c
>
> --
> 2.34.1
>